Abstract

Background: Several bacteria tolerate chromate with this attribute important in bacteria intended for biotechnological applications on chromate clean-up. Marine bacteria are beginning to show promise in this field due to their range and novelty. However, the general mechanisms of chromate tolerance employed by marine bacteria remain unknown.

Objective: To understand differential protein expression of a marine Staphylcoccus sp. in terms of response to hexavalent chromium stress.

Method: In this study, protein extracted from Staphylococcus xylosus grown in varying chromate (Cr (VI)) conditions (50, 100, 150 and 200 µg mL-1 Cr (VI)) was subject to spectral counting strategy where unlabelled protein samples were analyzed separately using the same protocol as each other, and the relative protein quantification was established by comparing the number of MS/MS spectra identified for each protein.

Results: A total of 613 proteins detected in S. xylosus were differentially expressed when grown in varying Cr (VI) conditions and were grouped functionally. Response in medium with 50 µg mL-1 Cr (VI) was not very different from that of the control (no Cr). Whereas, in medium with 200 µg mL-1 Cr (VI), the ability of S. xylosus to cope with Cr stress seemed to be reduced as the number of upregulated stress tolerant proteins (4) was less than those observed in medium with 150 µg mL-1 (15) or 100 µg mL-1 Cr (VI) (16). Up-regulation patterns showed that superoxide removal, directed DNA repair and proteins involved in peptide mis-folding were mechanisms employed by S. xylosus for surviving Cr induced stress in medium with 100 and 150 µg mL-1 Cr (VI).

Conclusion: These findings have important implications for understanding mechanisms of chromate tolerance, which provides new information of how a marine Staphylococcus deals with chromate toxicity.

Keywords: Staphyloccous xylosus, chromate, protein profiling, up-regulation, fold-change, LC-MS-QToF.

Graphical Abstract